THE MOLARS. 



635 



b. The ivory or dentine is deposited little by little upon the internal face of 

 the enamel, and soon fills, from the crown to the roots, the diverticula of the pulp 

 cavity. At first covered by the enamel, it soon becomes, under the influence of 

 wear, an integral part of the dental table. It is seen, in the superior molars, to 

 surround the periphery of the two infundibula and to constitute the basis of the 55 

 which their table resembles ; upon many of these teeth this comparison is so exact 

 that it is outlined by brown lines, sometimes very dark. In the inferior molars, 

 the dentine is found, so to speak, only upon the outer side of the infundibula ; 

 its central parts also have a brown coloration in a large number of subjects. 



c. The cement is extremely abundant upon the molars. It is this which 

 is directly applied upon the enamel, covers the faces, penetrates the notches, and 

 fills the infundibula. The tooth seems to become covered with it in proportion 

 as it is expelled from its socket, and at the level of its free extremity particularly, 

 for the radicular extremity only carries a thin layer ; but when the latter becomes 

 the surface of friction, in very old horses, it excites an abundant secretion of 

 radical cement, which consolidates it into its cavity of reception and considerably 

 augments the area of the dental table, as we have already seen a propos of the 

 structure of the incisors (Fig. 304). 



It is easy to account for the relations of the different layers which enter into 

 the composition of a molar, by making transverse sections of the latter parallel 



Fig. 305.— Transverse section of a superior left molar (enlarged). 



to the surface of friction. The enamel is there outlined by porcelain-white, 



sometimes vitreous, bands, the cement by very clear coffee-and-milk color, the 



dentine, finally, by darker coffee-and-milk color, always veined with darker lines. 



The accessory branch or loop, in the superior molars (Fig. 298), is always 



